Optical element and manufacturing method thereof

ABSTRACT

A flexible optical element useful for optical wiring is provided, in which a light emitting portion is disposed to a core end face of a flexible polymeric optical waveguide channel sheet having a film substrate clad, a core and a clad layer covering the core. A method which enables of manufacturing the optical element in a simple and convenient manner at a low cost is also provided.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to an optical element in which a light emittingportion is disposed to a flexible polymeric optical waveguide channeland a manufacturing method thereof.

2. Description of the Related Art

Methods of manufacturing polymeric waveguide channels proposed so farinclude, for example, (1) a method of impregnating a film with amonomer, selectively exposing a core portion to change the refractiveindex and bonding the film (selective polymerization method), (2) amethod of coating a core layer and a clad layer and then forming a cladportion by use of a reactive ion etching (RIE method), (3) a method ofusing photolithography of conducting exposure and development by use ofa UV-ray curable resin including a polymeric material with a lightsensitive material added therein (direct exposure method), (4) a methodof utilizing injection molding, and (5) a method of coating a core layerand a clad layer and then exposing the core portion to change therefractive index of the core portion (photo-bleaching method).

However, the selective polymerization method (1) involves a problem inbonding the film, the method (2) or (3) increases the cost because ofthe use of photolithography, and the method (4) has a problem in theaccuracy of the diameter for the obtained core. Further, the method (5)has a problem in that no sufficient difference for the refractive indexcan be obtained between the core layer and the clad layer.

At present, only the methods (2) and (3) are practically excellent inview of the performance but they involve the problem of the cost asdescribed above. Then, none of the methods (1) to (5) is suitable to theformation of the polymeric waveguide channel to a large-area, flexibleplastic substrate.

Further, as a method of manufacturing a polymeric optical waveguidechannel, a method of filling a polymer precursor material for core intoa pattern substrate (clad) in which a pattern of grooves as capillariesis formed, then curing the same to prepare a core layer and bonding aplanar substrate (clad) thereon has been known. However, since thepolymer precursor material is thinly filled and cured not only in thecapillary grooves but also between the pattern substrate and the planarsubstrate entirely to form a thin layer of a composition identical withthe core layer, it involves a problem that light leaks through the thinlayer.

As one method for overcoming the problems, David Hart has proposed amethod of manufacturing a polymeric optical waveguide channel bysecuring a patterned substrate in which a pattern of grooves ascapillaries is formed and a planar substrate by a clamping jig, thensealing a contact portion between the patterned substrate and the planarsubstrate with a resin, then decreasing the pressure and filling amonomer (diallylisophthalate) solution in the capillaries (JapanesePatent No. 3151364). This is a method of lowering the viscosity of thefilling material by use of a monomer instead of use of the polymerprecursor material as the core forming resin material, filling thematerial into the capillary by utilizing the capillary phenomenon whilekeeping the monomer from filling the portions other than the capillary.

However, since the method uses the monomer as the core forming material,it involves a problem that the volumic shrinkage is large when themonomer is polymerized into a polymer to increase the transmission lossof the polymeric optical waveguide channel.

Further, this is a complicated method of securing the patternedsubstrate and the planar substrate by clamping, or further seating thecontact portion with a resin, so that it is not suitable for massproduction and, as a result, the reduction of the cost cannot beexpected. Further, this method cannot be applied to the manufacture of apolymeric optical waveguide channel that uses a film in the thickness ofmm order or 1 mm or less as the clad.

Geroge M. Whitesides, et al. of Harvard University have recentlyproposed a method of a capillary tube micromold as one of lithographictechnics, as a new technology of preparing a nano-structure. This is amethod of preparing a master substrate by utilizing photolithography,transferring the nano-structure of the master substrate to apolydimethylsiloxane (PDMS) template by utilizing close adhesion andeasy releasability of PDMS and casting a liquid polymer into thetemplate by utilizing the capillary phenomenon and curing the same.Detailed illustrative descriptions are contained in SCIENTIFIC AMERICAN,September 2001 (Nikkei Science; December 2001).

Further, Kim Enoch, et al. in the group of George M. Whitesides ofHarvard University have filed, a patent application regarding acapillary tube micromold method (U.S. Pat. No. 6,344,198).

However, even when the manufacturing method described in the patent isapplied to the manufacture of the polymeric optical waveguide channel,since the cross sectional area of the core portion in the opticalwaveguide channel is small, it takes much time for forming the coreportion and is not suitable for mass production. Further, it has adrawback that the monomer solution causes a volumic change when it ispolymerized into a polymer, which changes the shape of the core toincrease the transmission loss.

Further, B. Michel, et al. of IBM Zurich Research Institute haveproposed a lithographic technology at high resolution using PDMS andreported that the technique can provide resolution at several tens nm.Detailed illustrative descriptions are contained in IBM J. REV. &DEV.vol. 45 No. 5, September 2001.

As described above, the soft lithographic technique or the capillarytube micromold method using PMDS is a technique which has recentlyattracted attention mainly in the United States as the nano-technology.

However, in the manufacture of the optical waveguide channel by use ofthe micromold method as described above, decrease of the volumicshrinkage during curing (accordingly, lowering of the transmission loss)and lowering of viscosity of the filled liquid (such as monomer) foreasier filling cannot be compatible with each other. Accordingly, whenpreferences is attached to the lowering of the transmission loss, theviscosity of the filled liquid cannot be lowered below a certain limit,which retards the filling speed and mass production cannot be expected.Furthermore, the micromold method is based on the premise of using glassor silicon substrates for the substrates and use of a flexible filmsubstrate is not taken into consideration.

By the way, in recent IC technology or LSI technology, attention hasbeen focused on conducting optical wiring between apparatuses, betweenboards in an apparatus and within chips for improving the operationspeed or the integration degree instead of conducting electric wiring athigh density.

As the device for optical wiring, Japanese Patent Laid Open No.2000-39530, for example, describes an optical element for a polymericoptical waveguide channel having a core and a clad surrounding the core,which has a light emitting element and a light receiving element in thedirection of laminating a core and a clad, and having an incident sidemirror for incidence of light from the light emitting element to thecore and an exit side mirror for emission of light from the core to thelight receiving element in which a clad layer is formed in a concaveshape at a portion corresponding to an optical channel from the lightreceiving element to the incident side mirror and from the exit sidemirror to the light receiving element to converge the light from thelight emitting element and the light from the exit side mirror. Further,Japanese Patent Laid-Open No. 2000-39531 describes an optical element inwhich light from the light emitting element enters the core end face ofa polymeric optical waveguide channel having a core and a cladsurrounding the core, wherein the light incident end face of the core isformed so as to provide a convex surface to the light emitting elementthereby converging the light from the light emitting element to suppressthe waveguide loss.

Further, Japanese Patent Laid-Open No. 2000-235127 describes aphotoelectronic integrated circuit in which a polymeric opticalwaveguide channel is assembled directly on a hybridized photoelectroniccircuit substrate in which electronic elements and light elements areintegrated.

By the way, when the element described above can be incorporated, forexample, by being bent into the apparatus in the optical wiring, thedegree of freedom for designing the assembling of the optical wiring canbe increased and, as a result, integration degree of IC or LSI can beimproved.

However, since both of the optical element and the photoelectronicintegrated circuit lack in the flexibility, it is impossible toincorporate the same, for example, by bending into the apparatus.Furthermore, since the optical element and the photoelectronicintegrated circuit have to be used with the core end face being formedinto a convex shape or use of the mirror together, this inevitablycomplicates structure. The reason for requiring formation of the coreend face into the convex shape or converging of light by use of a lensas described above is that since the semiconductor laser element as thelight emitting element used, for example, in the optical elementgenerates a great amount of heat and the heat can no more be dissipatedwhen the element is used merely in close adhesion with the polymericwaveguide channel to cause operation failure, it is necessary to providea gap between the polymeric waveguide channel portion and the lightemitting element to release heat while a diverging angle is present forthe spot of a semiconductor laser (accordingly, light diverges as thegap is larger to bring about a difficulty in confining light in theoptical waveguide channel).

Further, while both of the optical element and the photoelectronicintegrated circuit include the polymeric optical waveguide channel, bothare manufactured by utilizing the photolithographic method, whichcomplicates the structure, causes a problem such as liquid wastes andresults in large environmental loads.

As described above, the flexible polymeric optical waveguide channelsheet itself has not been provided at all so far and, in addition, anidea of connecting the light emitting element to the end face of thepolymeric optical waveguide channel sheet thereby forming an opticalelement used for light optical wiring to avoid loss of flexibility hasnot been proposed at all.

SUMMARY OF THE INVENTION

This invention has been achieved in view of the foregoing problems andintends to provide an optical element having flexibility which is usefulfor optical wiring. This invention also intends to provide a method ofmanufacturing an optical element of preparing the optical elementdescribed above by a simple and convenient method at an extremely lowcost.

According to an aspect of this invention, an optical element includes aflexible polymeric optical waveguide channel sheet having a cladincluding a flexible film substrate, a core of a curing product of aUV-ray curable resin or a thermosetting resin disposed on the clad and aclad layer formed so as to cover the core, and a light emitting portiondisposed to an end face of the optical waveguide channel sheet.

According to another aspect of this invention, a method of manufacturingan optical element has the steps of: forming a layer of atemplate-forming resin material to an original substrate in whichconvexes for optical waveguide channel are formed, then peeling the sameto form a mold, and then cutting both ends of the mold to exposeconcaves corresponding to the convexes for optical waveguide channelformed to the mold, thereby preparing a template; closely adhering aflexible film substrate for clad having good adhesion with the templateto the template; bringing one end of the template which is adhered withthe flexible film substrate for clad into intimate contact with a UV-raycurable resin or a thermosetting resin to form a core and making theUV-ray curable resin or the thermosetting resin intrude by a capillaryphenomenon to the concaves of the template; curing the intruded UV-raycurable resin or the intruded thermosetting resin and peeling thetemplate from the flexible film substrate for clad; and forming a cladlayer on the flexible film substrate for clad formed with the core,thereby preparing a flexible polymeric optical waveguide channel sheetand then attaching a light receiving portion to the core end face of thesheet.

DESCRIPTION OF THE ACCOMPANYING DRAWINGS

Preferred embodiments of this invention will be described in detailsbased on the followings, wherein:

FIG. 1 is a conceptional view illustrating an example of an opticalelement according to this invention;

FIGS. 2A-2G is a schematic view illustrating the steps of manufacturingan optical waveguide channel sheet of this invention; and

FIGS. 3A-3G is a schematic view illustrating other steps ofmanufacturing an optical waveguide channel sheet of this invention.

PREFERRED EMBODIMENT OF THE INVENTION

The optical element according to this invention includes a flexiblepolymeric optical waveguide channel sheet having a clad including aflexible film substrate, a core made of a curing product of a UV-raycurable resin or a thermosetting resin disposed on the clad and a cladlayer formed so as to cover the core, and a light emitting portiondisposed to a core end face of the optical waveguide channel sheet. Inthe optical element according to the invention, since no optical channelchanging device such as a lens or a mirror is required, it is extremelysimplified as the device. Further, in the optical element according tothe invention, since the flexible polymeric optical waveguide channelsheet is used and the light emitting portion is disposed to the end facethereof, flexibility is high over the entire device and the device canbe deformed easily such as by bending or can be incorporated in adeformed state into an integrated circuit to greatly enhance theintegration degree of the integrated circuit in conjunction with thesimplification of the element as described above.

The optical element according to this invention can be used for wideapplications such as optical wiring in various stages, for example,optical wiring between apparatuses, between boards in an apparatus andbetween chips in the board.

FIG. 1 shows an example of an optical element according to thisinvention as a conceptional view. Shown in FIG. 1 are an optical element1, a lower clad (flexible film substrate clad) 2, a core 4, a clad layer6, a light emitting portion 7 and a light receiving portion 8respectively.

Further, the method of manufacturing the optical element according tothis invention is conducted by preparing a flexible polymeric opticalwaveguide channel sheet and then attaching a light emitting portion to acore end face. The method of preparing the flexible polymeric opticalwaveguide channel sheet includes the following steps of:

1) forming a layer of a template-forming resin material to an originalsubstrate in which convexes for optical waveguide channels are formed,then peeling the same to form a mold and then cutting both ends of themold so as to expose concaves corresponding to the convexes for theoptical waveguide channel formed in the mold to prepare a template,

2) closely adhering a flexible film substrate for clad to form a cladhaving good adhesion with the template to the template,

3) bringing one end of the template closely adhered with the filmsubstrate for clad into contact with a UV-curable resin or athermosetting resin to form a core and making the UV-ray curable resinor the thermosetting resin intrude by a capillary phenomenon into theconcaves of the template,

4) curing the intruded UV-ray curable resin or the intrudedthermosetting resin and peeling the template from the flexible filmsubstrate for clad, and

5) forming a clad layer on the flexible film substrate for clad to whichthe core is formed.

The method of manufacturing the flexible polymeric optical waveguidechannel sheet according to this invention (hereinafter sometimesreferred to simply as an optical waveguide channel sheet) is based onthe finding that when a flexible film substrate for clad having goodadhesion with the template (hereinafter simply referred to as filmsubstrate for clad, film substrate, etc.) to the template as describedabove, the UV-ray curable resin or the thermosetting resin can be madeto intrude only into the concaves without causing a gap between thetemplate and the film substrate for clad except for the concavedstructure formed to the template even when both of them are not securedby use of a special unit (fixing unit as described in Japanese PatentNo. 3151364). The method of manufacturing the polymeric opticalwaveguide channel according to this invention is extremely simplified inview of the manufacturing steps, can manufacture the polymeric opticalwaveguide channel easily and enables manufacture of the polymericoptical waveguide channel at an extremely low cost compared with theexistent method of manufacturing the polymeric optical waveguidechannel. Further, the manufacturing method for the polymeric opticalwaveguide channel according to this invention can provide a flexiblepolymeric optical waveguide channel with less loss, at high accuracy andenabling easy attachment to various kinds of equipment. Further, themethod can freely set the shape and the like of the polymeric opticalwaveguide channel.

Then, in the method of manufacturing the optical element according tothis invention, since the light emitting portion may be merely attachedto the end face of the optical waveguide channel sheet manufactured asdescribed above, this is an extremely simple and convenient method andcapable of reducing the cost to such an extent as comparison withoptical elements using existent polymeric optical waveguide channels isunreasonable.

At first, the outline for the method of manufacturing the opticalwaveguide channel sheet according to this invention is to be explainedwith reference to FIG. 2.

FIG. 2A shows an original substrate to which convexes 12 for opticalwaveguide channel are formed. At first, as shown in FIG. 2B, a layer 20a of a template-forming resin material (for example, cured layer of acurable resin) is formed to the surface of the original substrate 10 towhich convexes 12 for optical waveguide channel are formed. Then, thelayer 20 a of the template-forming resin material is separated from theoriginal substrate 10 (mold transfer) and then both ends of the mold arecut so as to expose concaves 22 corresponding to the convexes foroptical waveguide channel formed to the mold to prepare a template 20(not illustrated) (refer to FIG. 2C).

A film substrate 30 for clad having good adhesion with the template isadhered closely to the thus prepared template (refer to FIG. 2D). Then,one end of the template is in contact with a curable resin 40 a and theresin is made to intrude into the concaves 22 of the template byutilizing the capillary phenomenon. FIG. 2E shows the state where thecurable resin is filled in the concaves of the template. Then, thecurable resin in the concaves is cured and then the template is peeled(not illustrated). As shown in FIG. 2F, convexes for optical waveguidechannels (cores) 40 are formed on the film substrate for clad.

Further, an optical waveguide channel sheet 60 according to thisinvention is manufactured by forming a core layer 50 to the core formingsurface of the film substrate for clad (refer to FIG. 2G).

Further, FIG. 3 shows an example of adhering a film as a clad on thefilm substrate to which the core is formed. From FIG. 3A to FIG. 3F arein common with the steps represented by FIG. 2A to FIG. 2F showing thesteps starting from the original substrate to the formation of the coreon the film substrate. FIG. 3G shows a step of bonding a film 52 to forma clad on the core forming the film substrate by use of an adhesive 54.

The method of manufacturing the optical waveguide channel sheetaccording to the invention will be explained in the sequence of thesteps.

1) Step of forming a layer of a template-forming resin material to anoriginal substrate in which convexes for optical waveguide channels areformed, then peeling the same to form a mold and then cutting both endsof the mold so as to expose concaves corresponding to the convexes foroptical waveguide channels formed to the mold, thereby preparing atemplate

<Preparation of Original Substrate>

For the preparation of the original substrate in which convexes foroptical waveguide channels (convexes corresponding to the core) areformed, an existent method, for example, a photolithographic method canbe used with no particular restriction. Further, a method ofmanufacturing a polymeric optical waveguide channel by anelectrodeposition method or a photoelectrodeposition method filedpreviously by the present applicant (Japanese Patent Laid-Open No.2002-333538) is also applicable to the preparation of the originalsubstrate. The size of the convexes for optical waveguide channelsformed to the original substrate is properly determined depending, forexample, on the application of the polymeric optical waveguide channel.Generally, in a case of an optical waveguide channel for use in singlemode, a core of about 10 μm square is used, while a core of about 50 to100 m square is used in a case of an optical waveguide channel for usein multimode, but an optical waveguide channel having an even largercore portion such as about several hundreds μm may also be utilizeddepending on the application.

<Preparation of Mold>

The mold is prepared by forming a layer of the template resin materialto the optical waveguide channel surface of the original substrateprepared as described above and peeling the same.

It is preferred that the template resin material can be peeled easilyfrom the original substrate and has mechanical strength and dimensionalstability at or above a certain level as the template (usedrepetitively). The layer of the template resin material is formed of atemplate-forming resin which may be optionally incorporated with variousadditives.

Since individual optical waveguide channels formed to the originalsubstrate have to be transferred accurately to the template-formingresin, the resin preferably has a viscosity at a certain limit or less,for example, about 2000 to 7000 mPa·s. Further, for controlling theviscosity, a solvent may be added to such an extent as the solvent givesno undesired effect.

For the template-forming resin, a curable silicone resin (thermosettingor room temperature curing type) is preferably used with a view point ofpeeling property, mechanical strength and dimensional stability.Further, the resin of the type described above and a liquid resin of lowmolecular weight is preferably used since a sufficient penetratingproperty is expected. The viscosity of the resin is preferably about 500to 7,000 mPa·s, and, further preferably, about 2000 to 5000 mPa·s.

As the curable silicone resin, those containing methyl siloxane group,ethyl siloxane group or phenyl siloxane group are preferred and acurable dimethyl siloxane resin is particularly preferred.

Further, it is desirable that releasing treatment such as coating of areleasing agent is applied in advance to the original substrate topromote releasing from the template.

The template resin material layer is formed to the optical waveguidechannel surface of the original substrate, for example, by forming alayer of a template-forming resin by a method of coating or casting thetemplate-forming resin to the surface and then applying drying treatmentor curing treatment as required.

The thickness for the template resin material layer is properlydetermined with the handleability as the template taken intoconsideration and, generally, it is appropriately about from 0.1 to 50mm.

Subsequently, the template resin material layer and the originalsubstrate are peeled to form a mold.

<Preparation of Template>

Then, both ends of the mold are cut so as to expose concavescorresponding to the convexes for optical waveguide channel formed tothe mold to prepare a template. The both ends of the mold are cut forexposing the concaves for making the UV-ray curable resin or thethermosetting resin intrude by the capillary phenomenon to the concavesof the template in the subsequent step.

It is preferred that the surface energy of the template is from 10dyne/cm to 30 dyne/cm, more preferably, within a range from 15 dyne to24 dyne/cm from a viewpoint of close adhesion with the substrate film.

Preferably, Share rubber hardness of the template is 15 to 80,preferably, 20 to 60 from a viewpoint of the mold forming performanceand the peeling property.

It is preferred that the surface roughness of the template (square meanroughness (RMS)) is 0.5 μm or less, preferably, 0.1 μm or less from aviewpoint of the mold formation performance.

2) Step of closely bonding film substrate for clad of good closeadhesion with template to template

Since the optical element according to this invention is used foroptical wiring in various stages, the material for the flexible filmsubstrate is selected depending on the application of the opticalelement while considering, for example, optical characteristics such asrefractive index and light transmittance, mechanical strength, heatresistance, adhesion with the template and flexibility. The film caninclude, for example, cycloaliphatic acrylic film, cycloaliphatic olefinfilm, cellulose triacetate film and fluoro resin-containing films. It isdesirable that the refractive index of the film substrate is less than1.55 and, preferably, less than 1.53 in order to ensure the differenceof the refractive index with respect to that of the core.

As the cycloaliphatic acryl film, OZ-1000, OZ-1100 and the like in whichalicyclic hydrocarbon such as tricyclodecane is introduced into theester substituents are used.

Further, the cycloaliphatic olefin film can include those having anorbornene structure in the main chain and those having a norbornenestructure in the main chain and having polar groups such as alkyloxycarbonyl group (alkyl groups of 1 to 6 carbon atoms or cycloalkylgroups) on the side chain. Among them, the cycloaliphatic olefin resinshaving the norbornene structure in the main chain as described above andpolar groups such as alkyloxy carbonyl groups on the side chain areparticularly suitable for the manufacture of the optical waveguidechannel sheet of this invention since they have excellent opticalcharacteristics such as a low refractive index (refractive index ofabout 1.50, and capable of ensuring the difference of refractive indexto that of the core and clad) and high optical transmittance, and areexcellent in close adhesion with the template as well as in heatresistance.

Further, the thickness of the film substrate is selected withflexibility, rigidity and easy handlability taken into considerationand, generally, it is preferably about 0.1 mm to 0.5 mm.

3) Step of bringing one end of template adhered with film substrate forclad into contact with UV-ray curable resin or thermosetting resin ascore and making UV-ray curable resin or thermosetting resin intrude bycapillary phenomenon into concaves of mold

In this step, for filling the UV-ray curable resin and the thermosettingresin by the capillary phenomenon into a gap formed between the mold andthe film substrate (concaves of the template), it is necessary that theUV-ray curable resin and the thermosetting resin used have a sufficientlow viscosity to enable filling and that the refractive index of thecurable resin after curing is higher than that of the polymeric materialconstituting the clad (0.02 or more of difference to that of the clad).In addition, for reproducing at high accuracy an original shape of theconvexes for optical wave guide channel formed to the originalsubstrate, it is necessary that the volumic change of the curable resinbefore and after curing is small. For example, decrease in the volumecauses waveguide loss. Accordingly, it is desirable for the curableresin that the volumic change is as little as possible and it isdesirably 10% or less, preferably, 6% or less. Lowering of the viscosityby the use of a solvent is preferably avoided since this increases thevolumic change before and after curing.

Accordingly, it is preferred that the viscosity of the curable resin isfrom 10 mPa·s to 2000 mPa·s, preferably, 20 mPa·s to 1000 mPa·s and,further preferably, 30 mPa·s to 500 mPa·s.

Further, epoxy type, polyimide type, UV-ray curable acryl type resinsare used preferably as the UV-curable resin.

Further, in this step, for promoting the filling of the UV-ray curableresin or the thermosetting resin by the capillary phenomenon to theconcaves of the mold by bringing one end of the template adhered withthe film substrate into contact with the curable resin or thethermosetting resin as a core, it is desirable that the entire system isdepressurized (to about 0.1 to 2000 Pa). Instead of depressurizing theentire system, it may be sucked by a pump from an end different from theone in contact with the curable resin, or it may be pressurized at oneend in contact with the curable resin.

Further, for promoting the filling, it is also an effective measure tofurther lower the viscosity of the curable resin by previously heatingthe curable resin to be in contact with one end of the template insteadof or in addition to the depressurization or pressurization describedabove.

It is necessary that the refractive index of the curing product of theUV-ray curable resin or the thermosetting resin of the core is greaterthan that of the film substrate as the clad (including the clad layer inthe subsequent step (5)) and it is 1.53 or, more preferably, 1.55 ormore. The difference of the refractive index between the clad (includingthe clad layer in the subsequent step (5)) and the core is 0.02 or moreand, preferably, 0.05 or more.

4) Step of curing intruded UV-ray curable resin or thermosetting resinand peeling template from film substrate

The intruded UV-ray curable resin or the thermosetting resin is cured.For curing the UV-ray curable resin, UV-ray lamp, UV-ray LED or UV rayirradiation apparatus and the like are used. Further, for curing thethermosetting resin, heating in an oven is adopted.

Further, the template used in the steps (1) to (3) above can also beused as it is as the clad layer, in which it is not necessary to peelthe template and it can be used as it is as the clad layer.

5) Step of forming clad layer on film substrate formed with core

A clad layer is formed on a film substrate formed with a core. The cladlayer includes, for example, films (for example, a film substrate asused in the preceding step (2) is used in the same manner), layersformed by coating and curing curable resins (UV-ray curable resins,thermosetting resins) and polymeric films obtained by coating and dryinga solvent solution of a polymeric material. When the film is used as theclad layer, the film is bonded by use of an adhesive in which therefractive index of the adhesive is preferably near to the refractiveindex of the film.

The refractive index of the clad layer is, preferably, 1.55 or less and,more preferably, 1.53 or less for ensuring the difference of therefractive index relative to that of the core. Further, it is preferredthat the refractive index of the clad layer is equal with the refractiveindex of the film of the substrate from a viewpoint of confinement oflight.

In the manufacturing method of the optical waveguide channel sheetaccording to this invention, combined use of a thermosetting siliconeresin, in particular, a thermosetting dimethyl siloxane resin as thetemplate material and a cycloaliphatic olefin resin having a norbornenestructure in the main chain and having polar groups such as alkyloxycarbonyl groups on the side chain as the film material providesparticularly high adhesion between both of them and can fill theconcaves with the curable resin rapidly by the capillary phenomenon evenwhen the cross sectional area of the concaves is extremely small (forexample, 10×10 μm rectangular shape).

Further, the template can also be used as the clad layer, in which it ispreferred that the refractive index of the template is 1.5 or less andthe template is, applied with ozone treatment for improving the adhesionbetween the template and the core material.

Then a light emitting portion is attached to the core end face of theoptical waveguide channel sheet prepared as described above. Forimproving the integration degree of an integrated circuit, a surfacelight emitting laser array (VCSEL) is used preferably for the lightemitting portion.

Since a semiconductor laser device of the surface light emitting laserarray generates a great amount of heat, it is necessary to keep adistance between the semiconductor laser device and the core end face inorder to prevent undesired effects by the heat generation. However,since the semiconductor laser beam has a diverging angle, when thedistance exceeds a certain limit, the laser beam spot diameter at thecore end face exceeds an allowable value for the core (for example, theallowable diameter is 45 μm for a core diameter of 50 μm).

However, with the spot diameter of the semiconductor laser and thediverging angle of the laser beam in the surface light emitting lasertaken into consideration, the semiconductor layer and the core end facecan be spaced apart to such an extent as sufficiently avoiding theeffect of heat generation without using the lens or the like.

For example, in a case of attaching a surface light emitting laser arraywith a spot diameter of the semiconductor laser of 10 μm, the beamdiverging angle of 25° and an array distance of 250 μm (VCSEL-AM-0104,manufactured by Fuji Xerox Co., Ltd.) to the end face of a multimodepolymeric optical waveguide channel sheet with the core diameter of 50μm, since the laser beam spot diameter at the core surface is allowableto about 45 μm, the semiconductor layer and the core end face can bespaced apart up to 79 μm as the maximum. When the laser beam diameter atthe core end face is set to 30 μm, the distance between thesemiconductor laser and the core end face is about 45 μm. With such anextent of the distance, generated heat can be released sufficiently evenwhen considering the temperature elevation of the semiconductor laserdevice up to about 100° C.

Accordingly, a laser array in which the spot diameter of thesemiconductor laser is 1 to 20 μm and the diverging angle of the laserbeam is about 5° to 30° in the surface light emitting laser array isused preferably. The array distance is preferably about 100 to 500 μm.For example, VCSEL-AM-0104, VCSEL-AM-0112 and the like manufactured byFuji Xerox Co., Ltd. are used preferably.

Further as a unit that keeps the distance between the core end face ofthe optical waveguide channel sheet and the semiconductor laser of thesurface light emitting laser array as described above, a frame of asufficient height to keep the distance may be disposed to the surface ofthe light emitting laser array, and the frame and the optical waveguidechannel sheet are fixed, for example, by use of adhesives.

Further, in the optical element according to this invention, a lightreceiving portion may be disposed in addition to the light emittingportion. A photodiode array or the like is used preferably as the lightemitting portion. For the photodiode array, those having a sensitivityin the same ultraviolet wavelength as the surface light emitting laserarray and having high sensitivity such as Si photodiode array or GaAsphotodiode array are preferred.

EXAMPLES

This invention is to be explained more specifically with reference toexamples but the invention is not restricted to such examples.

Example 1

After coating a thick film resist (SU-8, manufactured by MicrochemicalCo.) to an Si substrate by a spin coating method, it was prebaked at 80°C., exposed through a photomask and developed to form four convexes eachof a square cross section (width: 50 μm, height: 50 μm) as shown in FIG.1. The distance between each of the convexes was set to 250 μm. Then, itwas postbaked at 120° C. to prepare an original substrate formanufacturing an optical waveguide channel core.

Then, after coating a releasing agent to the original substrate, athermosetting dimethyl siloxane resin (SYLGARD 184, manufactured by DowCorning Asia Co.) was cast and cured by heating at 120° C. for 30minutes and then peeled to prepare a mold having concaves correspondingto the convexes of the square cross section (mold thickness: 3 mm).Further, both ends of the mold were cut to prepare an input/outputportion for the following UV-ray curable resin to form a template.

The template and a film substrate of 188 μm thickness (ARTON film,manufactured by Nippon Synthesis Rubber Co., refractive index: 1.510)slightly larger than the template were adhered closely. Then, when aUV-ray curable resin at a viscosity of 1300 mPa·s (PJ3001, manufacturedby JSR Co.) was dripped by several drops to the input/output portion atone end of the template, the concaves were filled with the UV-raycurable resin by the capillary phenomenon. Then, the upper portion ofthe template was irradiated with UV-light at 50 mW/cm² for 5 minutes toconduct UV curing. When the template was peeled from the ARTON film, acore of the same shape as that of the convexes of the original substratewas formed on the ARTON film. The refractive index of the core was1.591.

Then, after coating a UV-ray curable resin having a refractive indexafter curing of 1.510 which is identical with that of the ARTON film(manufactured by JSR Co.) over the entire core forming surface of theARTON film, w-light at 50 mW/cm² was applied for 5 minutes to conductUV-ray curing (film thickness after curing was 10 μm). A flexibleoptical waveguide channel sheet (50 mm×300 mm) was obtained. The loss ofthe polymeric optical waveguide channel was 0.33 dB/cm.

Then, a 1×4 surface light emitting laser array (VCSEL-AM-0104,manufactured by Fuji Xerox Co., Ltd., with a spot diameter of thesemiconductor laser of 10 μm, a beam diverging angle of 25° and an arraydistance of 250 μm) was attached to the core end face of the opticalwaveguide channel sheet prepared as described above at a gap of 50 μm toform a flexible polymeric waveguide channel with the surface lightemitting laser array.

Example 2

An original substrate for preparing an optical waveguide channel havingfour convexes each of a square cross section (width: 50 μm, height: 50μm) was by the same method as in Example 1. Then, after preparing a moldin the same manner as in Example 1, both ends were cut to form atemplate. The template and an ARTON film (thickness: 180 μm) slightlylarger than the template were closely adhered and, when several drops ofa thermosetting resin at a viscosity of 500 mPa·s (manufactured by JSRCo.) were dripped to the input/output portion at one end of thetemplate, the concaves were fill with the thermosetting resin by thecapillary phenomenon. It was thermally cured by heating for 30 minutesin an oven at 130° C. When the template was peeled from the ARTON film,a core of the same shape as the original substrate convexes was formedon the ARTON film. The refractive index of the core was 1.570. Further,after coating, a thermosetting resin with the refractive index aftercuring being identical with the ARTON film (manufactured by JSR Co.)over the entire surface of the core forming surface of the ARTON film,it was heat (film thickness after curing: 10 μm). A flexible opticalwaveguide channel sheet (50 mm×300 mm) was obtained. The loss of thepolymeric optical waveguide channel was 0.33 dB/cm.

Then, a 1×4 surface light emitting laser array (VCSEL-AM-0104,manufactured by Fuji Xerox Co., Ltd.) was attached at a 50-μm gap to thecore end face of the optical waveguide channel sheet prepared asdescribed above to form a polymeric waveguide channel with the surfacelight emitting laser array.

Example 3

An original substrate for preparing an optical waveguide channel havingfor convexes each of a square cross section (width: 50 μm, height: 50μm) by the same method as in Example 1. Then, after preparing a mold inthe same manner as in Example 1, both ends were cut to form a template.The template and an ARTON film (thickness: 180 μm) slightly larger thanthe template were closely adhered and several drops of a thermosettingresin at a viscosity of 1300 mPa·s (PJ3001, manufactured by JSR Co.)were dripped to the input/output portion at one end of the template. Thetemplate and ARTON film were adhered closely, which were placed in acontainer depressurized by a vacuum pump (1.0 Pa). The UV-ray curableresin was filled into the concaves instantly by the capillaryphenomenon. After taking out the same from the container, the upperportion of the template was irradiated with UV-light at 50 mW/cm² for 5minutes to conduct curing and the template was peeled. A core with arefractive index of 1.591 was formed on the ARTON film.

Further, after coating a thermosetting resin with the refractive indexafter curing of 1.510 which is identical with that of the ARTON film(manufactured by JSR Co.) over the entire surface of the core formingsurface of the ARTON film, it was cured by applying UV-rays of 50 mW/cm²for 10 minutes (film thickness after curing: 10 μm). A flexible opticalwaveguide channel sheet (50 mm×300 mm) was obtained. The loss of thepolymeric optical waveguide channel was 0.33 dB/cm.

Then, a 1×4 surface light emitting laser array (VCSELAM-0104,manufactured by Fuji Xerox Co., Ltd.) was attached at a 50-μm gap to thecore end face of the optical waveguide channel sheet prepared asdescribed above to form a flexible polymeric waveguide channel with thesurface light emitting laser array.

Example 4

A flexible optical waveguide channel sheet (50 mm×300 mm) was preparedin the same manner as in Example 3, except for closely adhering atemplate to an ARTON film, sucking from one end of the input/outputportion of the template by a diaphragm type suction pump (maximumsuction pressure: 33.25 KPa) instead of dripping several drops of theUV-ray curable resin to the input/output portion at the other end of thetemplate and placing the same in a container depressurized by the vacuumpump in Example 3. The loss of the polymeric optical waveguide channelwas 0.33 dB/cm.

Then, a 1×4 surface light emitting laser array (VCSEL-AM-0104,manufactured by Fuji Xerox Co., Ltd.) was attached at a 50-μm gap to thecore end face of the optical waveguide channel sheet prepared asdescribed above to form a flexible polymeric waveguide channel with thesurface light emitting laser array.

Example 5

The steps up to formation of the core on the ARTON film in Example 1were conducted by the same procedures.

Then, the ARTON film (thickness: 188 μm) was bonded to the core formingsurface of the ARTON film by use of an adhesive at a refractive index of1.510 (manufactured by JSR Co.) to prepare a flexible optical waveguidechannel sheet The loss of the polymeric waveguide channel was 0.33dB/cm.

Then, a 1×4 surface light emitting laser array (VCSEL-AM0104,manufactured by Fuji Xerox Co., Ltd.) was attached at a 50-μm gap to thecore end face of the optical waveguide channel sheet (50 mm×30 mm)prepared as described above to form a flexible polymeric waveguidechannel with the surface light emitting laser array.

Example 6

A template was prepared by the same method as in Example 1. Then, thetemplate and an ARTON film (thickness: 188 μm) slightly larger than thetemplate were adhered closely. Several drops of a UV-ray curable resinat a viscosity of 100 mPa·s (manufactured by NTT-AT Co.) were dripped byto the input/output portion at one end of the template. When suction wasconducted by a vacuum pump from the other end of the input/outputportion of the template, the concaves were filled with a UV-ray curableresin by the capillary phenomenon. Then, the upper portion of thetemplate was irradiated with UV-light at 50 mW/cm² for 5 minutes toconduct UV-ray curing. When the template was peeled from the ARTON film,a core of the same shape as the original base convexes was formed on theARTON film. The refractive index of the core was 1570.

Then, an ARTON film (188 μm thickness) was bonded to the core formingsurface of the ARTON film by use of an adhesive at a refractive index of1.510 (manufactured by JSR Co.) to prepare a flexible optical waveguidechannel sheet (50 mm×300 mm). The loss of the polymeric opticalwaveguide channel was 0.15 dB/cm.

Then, a 1×4 surface light emitting laser array (VCSEL-AM-0104,manufactured by Fuji Xerox Co., Ltd.) was attached at a 5 μm gap to thecore end face of the optical waveguide channel sheet prepared asdescribed above to form a flexible polymeric waveguide channel with thesurface light emitting laser array.

Example 7

An optical waveguide channel sheet (50 mm×300 mm) was prepared in thesame manner as in Example 1 except for heating the UV-ray curable resinin advance to 70° C., dripping several drops of the resin to theinput/output portion at one end of the template and then irradiating thesame with UV-rays after lowering the temperature to the room temperaturein Example 1. The loss of the polymeric optical waveguide channel was0.35 dB/cm.

Then, a 1×4 surface light emitting laser array (VCSEL-AM-0104,manufactured by Fuji Xerox Co., Ltd.) was attached at a 50-μm gap to thecore end face of the optical waveguide channel sheet prepared asdescribed above to form a polymeric waveguide channel with the surfacelight emitting laser array.

Since the optical channel changing device such as a lens or a mirror isnot necessary, the optical element according to this invention can besimplified extremely as a device. Further, since the flexible polymericoptical waveguide channel sheet is used and the light emitting portionis disposed to the end face thereof, the entire device has highflexibility and can be deformed simply by bending and the like. Further,it can be incorporated in a deformed state into an integrated circuitand can improve the integration degree of the integrated circuit greatlyin conjunction with the simplification of the device.

The optical element according to this invention can be used for wideapplications such as optical wiring in various states, for example,optical wiring between apparatuses, between boards in an apparatus andbetween chips in a board.

Further, in the manufacturing method of the optical element according tothis invention, since it can be conducted by merely preparing a flexiblepolymeric optical waveguide channel sheet by an extremely simplified andlow-cost method and then attaching the light emitting portion to the endface of the flexible polymeric optical waveguide channel sheet, this isan extremely simple and convenient method and can attain cost reductionto such an extent as comparison with optical elements using the existentpolymeric optical waveguide channels is unreasonable.

The entire disclosure of Japanese Patent Application No. 2002-187474filed on Jun. 27, 2002 including specification, claims, drawings andabstract is incorporated herein by reference in its entirety.

1. A method of manufacturing an optical element comprising the steps of:forming a layer of a template-forming resin material to an originalsubstrate in which convexes for optical waveguide channel are formed,then peeling the same to form a mold, and then cutting both ends of themold to expose concaves corresponding to the convexes for opticalwaveguide channel formed to the mold, thereby preparing a template;closely adhering a flexible film substrate for clad having good adhesionwith the template to the template; bringing one end of the templatewhich is adhered with the flexible film substrate for clad into intimatecontact with a UV-ray curable resin or a thermosetting resin to form acore and making the UV-ray curable resin or the thermosetting resinintrude by a capillary phenomenon into the concaves of the template;curing the intruded UV-ray curable resin or the intruded thermosettingresin and peeling the template from the flexible film substrate forclad; and forming a clad layer on the flexible film substrate for cladformed with the core, thereby preparing a flexible polymeric opticalwaveguide channel sheet and then attaching a light receiving portion tothe end face of the sheet.
 2. A method of manufacturing an opticalelement according to claim 1, wherein the clad layer is formed bycoating and then curing the UV-ray curable resin or the thermosettingresin.
 3. A method of manufacturing an optical element according toclaim 1, wherein the clad layer is formed by bonding a film for clad byuse of an adhesive having a refractive index which is nearly equal withthat of the film.
 4. A method of manufacturing an optical elementaccording to claim 1, wherein the layer of the template-forming resinmaterial is a layer formed by curing a curable silicone resin.
 5. Amethod of manufacturing an optical element according to claim 1, whereinsurface energy of the template is from 10 dyne/cm to 30 dyne/cm.
 6. Amethod of manufacturing an optical element according to claim 1, whereinShare rubber hardness of the template is from 15 to
 80. 7. A method ofmanufacturing an optical element according to claim 1, wherein surfaceroughness of the template is 0.5 μm or less.
 8. A method ofmanufacturing an optical element according to claim 1, wherein lighttransmittance of the template is 80% or more in a region from 350 nm to700 nm.
 9. A method of manufacturing an optical element according toclaim 1, wherein a thickness of the template is from 0.1 mm to 50 mm.10. A method of manufacturing an optical element according to claim 1,wherein a refractive index of the flexible film substrate for clad is1.55 or less.
 11. A method of manufacturing an optical element accordingto claim 1, wherein the flexible substrate for clad comprises acycloaliphatic olefin resin film.
 12. A method of manufacturing anoptical element according to claim 11, wherein the cycloaliphatic olefinresin film is a resin film having a norbornene structure in a main chainand having polar groups in side chains.
 13. A method of manufacturing anoptical element according to claim 1, wherein a pressure in a system isreduced in the step of making the UV-ray curable resin or thethermosetting resin intrude by the capillary phenomenon into theconcaves of the template.
 14. A method of manufacturing an opticalelement according to claim 1, wherein a viscosity of the UV-ray curableresin or the thermosetting resin is from 10 mPa·s to 2000 mPa·s.
 15. Amethod of manufacturing an optical element according to claim 1, whereina diameter of the core is within a range from 10 μm to 500 μm.